After his high-school exit exam he was conscripted, in summer 1938, to the Polish military service as cadet; next year, after the Invasion of Poland he was wounded during the Battle of Bzura. Soon he was imprisoned in a German POW camp, from which he tried to escape three times, finally succeeding in 1944. He moved to Kraków, where he became one of the students of the underground university. After the war, in the People's Republic of Poland, although at first he opposed the Polish communist government, in 1949 he joined the Polish United Workers' Party and was allowed to become a staff member of the University of Wrocław. Years later, a few days before his mysterious death, he told the listeners – group of his apprentices and co-workers in the University – that in 1949 he 'allowed himself to be manipulated'. Around 1951/1952 he defended his PhD thesis. In 1955 he became a docent, and in 1962 he became professor. However from the 1960s he became increasingly critical of the government. In the aftermath of the Polish 1968 political crisis, the Prague Spring and the Polish 1970 protests, where he openly supported the opposition, he was persecuted by the Polish secret police, Służba Bezpieczeństwa, and in the period of 1970-1972 he was forced to retire from Wrocław University, and briefly worked at the new University of Silesia. In 1972 he returned to Wrocław, as the environment there became more open again, while the Silesian University became a party stronghold, with Zieliński's research criticized for not being "proletarian" enough, and his refusal to bow down to the nomenklatura and accept the children of party officials as his students, irrespective of merit. He supported the Solidarity movement created in 1980. cemetery at Grabiszyn-Grabiszynek His death in the early morning hours of 6 March 1981 was suspicious: he was found dead on a sidewalk near his house. Although at first both the press and milicja investigators talked about a murder, from the next day the official line was that it was an accident and the investigation was annulled.
"Liczba Polaków w Niemczech w latach 1918-1939 na tle systemu niemieckiej statystyki narodowościowej" ; in: "Przegląd Zachodni" z.9,
"Polacy i polskość Ziemi Złotowskiej w latach 1918-1939"
"Zagadnienie powstań śląskich" ; in: "Wiadomości Historyczne" nr 5i nr 1
"Położenie i walka górnośląskiego proletariatu w latach 1918–1922"
Znaczenie traktatu wersalskiego dla rozwoju stosunków polsko-niemieckich"; in: "Kwartalnik Historyczny" nr 1,
"Polska myśl polityczna a sprawa ziem zachodnich " ; in: "Sobótka" nr 1-2
"Historia Polski 1864–1939"
"Rola powstania wielkopolskiego oraz powstań śląskich w walce o zjednoczenie ziem zachodnich i niepodległą Polskę " ; in: Droga przez półwiecze. O Polsce lat 1918-1968. Referaty z sesji PAN i UW poświęcone 50 rocznicy odzyskania niepodległości,
"Batalii podręcznikowej ciąg dalszy " ; in: "Odra", nr 10,
"O potrzebie i trudnościach badania polskiej myśli politycznej" ; in: "Polska Myśl polityczna XIX i XX w.", t.I: "Polska i jej sąsiedzi", Wrocław
"Polska Myśl polityczna XIX i XX w.", t.I: "Polska i jej sąsiedzi", Wrocław,
"Czy istniał model polskiego działacza politycznego " ; in: Dzieje kultury politycznej w Polsce pod red. J.A.Gierowskiego,
"Polska myśl polityczna XIX i XX wieku", t.II: "Twórcy polskiej myśli politycznej", Wrocław,